A typical stereo audio system comprises several audio signal sources such as a CD player and a tuner. The source units are generally arranged in a stack together with a selector and amplifier unit. In use, a signal from a selected source is amplified and provided to speakers which are typically located some distance away from the unit within the same room. The system controls are manually operable switches and dials on the signal sources and amplifier. There is sometimes a hand-held control device which is used to transmit infrared signals to the selector and amplifier unit.
In sophisticated systems several sets of speakers may be mounted in different rooms throughout a house. Sometimes the selector and amplifier unit will be provided with switches to enable different sets of speakers to be activated and deactivated. To power multiple speakers from a single amplifier an impedance matching device is also required.
The amplifier's volume control, which controls the volume level in the main room, also controls the volume level of the speakers in remote rooms. The remote rooms may have an attenuator device to reduce volume level but this attenuator can only reduce the volume below the level set by the amplifier. The attenuator cannot increase the amplifier's output.
The quality of the components and the weight and quality of the cabling can easily affect the quality of the sound output by the speakers. These systems also require specialist knowledge in the installation of the cabling and the audio components.